Enlargement of the European Union

The European Union (EU) has expanded a number of times throughout its history by way of the accession of new member states to the Union. To join the EU, a state needs to fulfil economic and political conditions called the Copenhagen criteria (named after the Copenhagen summit in June 1993), which require a stable democratic government that respects the rule of law, and its corresponding freedoms and institutions. According to the Maastricht Treaty, each current member state and the European Parliament must agree to any enlargement. The process of enlargement is sometimes referred to as European integration. This term is also used to refer to the intensification of co-operation between EU member states as national governments allow for the gradual harmonisation of national laws.

The EU's predecessor, the European Economic Community,^[1] was founded with the Inner Six member states in 1958, when the Treaty of Rome came into force. Since then, the EU's membership has grown to twenty-seven, with the latest member state being Croatia, which joined in July 2013. The most recent territorial enlargement of the EU was the incorporation of Mayotte in 2014. Campione d'Italia joined the EU Customs Union in 2020. The most notable territorial reductions of the EU, and its predecessors, have been the exit of Algeria upon independence in 1962, the exit of Greenland in 1985, and the withdrawal of the United Kingdom in 2020.

Accession negotiations are currently ongoing with Montenegro (since 2012), Serbia (since 2014), Albania (since 2020), North Macedonia (since 2020), Moldova (since 2024) and Ukraine (since 2024). Negotiations with Turkey were opened in October 2005,^[2] but have been effectively frozen by the EU since December 2016,^[3][4][5] due to backsliding in the areas of democracy, rule of law, and fundamental rights.^[3][6][7]

Bosnia and Herzegovina and Georgia were granted official candidate status respectively in December 2022^[8][9] and December 2023,^[10] but were asked to complete additional reforms before qualifying for the formal start of membership negotiations. Kosovo submitted an application for membership in December 2022.^[11] For Kosovo to be granted official candidate status, the Council will need to unanimously agree to start Kosovo's accession process by requesting an opinion from the European Commission on its application. The EU however remains divided on its policy towards Kosovo, with five EU member states not recognising its independence.